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Friendly bacteria to the rescue

THE “good” bacteria that inhabit our guts are more beneficial than we imagined. As well as crowding out dangerous organisms, they also release molecules that may protect us against inflammatory diseases, such as colitis.

Dennis Kasper at Harvard Medical School and his colleagues found that mice inoculated with Bacteroides fragilis – a human gut bug that produces a molecule called PSA – were able to fend off colitis provoked by the pathogenic bacterium Helicobacter hepaticus. Mice inoculated with strains that could not produce PSA, however, succumbed (Nature, vol 453, p 620).